1. Field of the Invention
The present invention relates generally to breathing regulators for use with demand breathing systems in diving, such as scuba diving, and more particularly to regulators for such systems in which the quantity of air or other gas or gaseous mixtures supplied to the user is determined by the breathing demands of the user and is adjustable by the user during such use.
2. Prior Art
Demand breathing systems used for diving, particularly scuba diving, typically employ a tank of breathable air or other breathable gaseous mixture (hereinafter referred to as "air" for the sake of brevity), a valve at the tank reducing the pressure of the mixture to approximately 140 psi as a first stage of regulating the pressure, a regulator to further reduce and control the pressure of the air in accordance with the breathing demand of the user as a second stage regulation, and a mouthpiece pneumatically coupled to the regulator through which the user breathes and receives air from the system. Typically the regulator employs a flexible diaphragm which senses the breathing demand of the user, and upon inhalation, the diaphragm is deflected in a first direction, opening a valve within the regulator to admit air from the tank valve to the mouthpiece and to the user. Upon exhalation, the exhaled air passing through the mouthpiece and into the regulator increases the pressure, deflecting the diaphragm in a second or opposite direction causing the valve within the regulator to close, and due to the increased pressure in the regulator, a portion of the air within the regulator is exhausted, equalizing the pressure on the diaphragm. Air can be exhausted by deflection of the diaphragm or a portion thereof away from its seat and exhausted between the diaphragm and its seat or through a separate exhaust valve.
Improvements on the typical demand breathing systems have been made to reduce or control the extent of the breathing demand required to open or crack the valve within the regulator and exhaust exhaled air, particularly where the conditions, such as depth of diving, changes the demand required as compared to ambient or surface or near surface conditions.
Such improvements have included the provision of a conical platform for the diaphragm to provide a varying effective area and permit the diaphragm to function as an exhaust valve, as in U.S. Pat. No. 4,147,176 to Christianson. U.S. Pat. No. 4,147,176 also provides an aspirator opening downstream of the valve in the regulator to direct the airflow, and in one embodiment provides for adjustment of the direction of the airflow by the user. However, in the arrangement disclosed in the patent, the user may adjust the direction of the airflow to obtain a favorable breathing demand during one portion of the breathing cycle, but in so doing may cause misadjustment, uncomfortable or even difficult operation during another portion of the breathing cycle.
Another attempted improvement is disclosed in U.S. Pat. No. 4,796,618 to Garraffa, in which an adjustable flow vane is provided in the flow of air toward the mouthpiece to deflect a portion of that flow toward or away from the mouthpiece. In the arrangement disclosed in U.S. Pat. No. 4,796,618, the vane can be adjusted between extremes by the user to substantially defeat the assisting effect of the directing of the airflow on the breathing demand required of the user. Such defeat of the assisting effect can cause uncomfortable breathing demand or difficulty in breathing by the user. A disadvantage of this arrangement is that the deflecting of a portion of the main air stream away from the mouthpiece may impede the delivery of air to the user.
Therefore, there is a need for adjusting apparatus for demand breathing systems which provides for selectively assisting the breathing demand of the user during substantially all of the breathing cycle, and which provides for selective adjustment by the user of the demand requirement and smooth operation of the system during its use.